v18.2.4
doc/radosgw: update QAT acceleration to specify the configuration
doc/install: update "update submodules"
doc/install: update "Official Releases" sources
ceph.spec.in: add support for openEuler OS
doc: update canonical tarballs URL
docs: Add information about OpenNebula integration
doc/install/index_manual: remove cephadm from toctree
doc/install: Update about ninja
doc: use plantweb as fallback of sphinx-ditaa
doc/install: add manual RADOSGW install procedure
doc/install: Remove Upstart from Freebsd deployment
doc: Remove inactive Ceph mirrors.
doc: reorganize Windows docs
doc/cephfs: update Dokany requirement
doc,man: typos found by codespell